U.S. patent application number 15/659434 was filed with the patent office on 2018-04-05 for electrode and device employing the same.
This patent application is currently assigned to Industrial Technology Research Institute. The applicant listed for this patent is Industrial Technology Research Institute. Invention is credited to Wen-Sheng CHANG, Kuang-Yao CHEN, Chien-Chih CHIANG, Ting-Wei HUANG, Chun-Hsing WU, Chang-Chung YANG.
Application Number | 20180097236 15/659434 |
Document ID | / |
Family ID | 59974241 |
Filed Date | 2018-04-05 |
United States Patent
Application |
20180097236 |
Kind Code |
A1 |
CHEN; Kuang-Yao ; et
al. |
April 5, 2018 |
ELECTRODE AND DEVICE EMPLOYING THE SAME
Abstract
An electrode and a device employing the same are provided. The
electrode includes a main body, and an active material. The main
body includes a cavity and is made of a conductive network
structure. In particular, the active material is disposed in the
cavity, wherein the length of the longest side of the particle of
the active material is greater than the length of the longest side
of the pore of the conductive network structure such that the
active material is confined in the conductive network
structure.
Inventors: |
CHEN; Kuang-Yao; (Ji'an
Township, TW) ; HUANG; Ting-Wei; (Hsinchu City,
TW) ; CHIANG; Chien-Chih; (New Taipei City, TW)
; WU; Chun-Hsing; (Taipei City, TW) ; YANG;
Chang-Chung; (Taipei City, TW) ; CHANG;
Wen-Sheng; (Pingtung City, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Industrial Technology Research Institute |
Hsinchu |
|
TW |
|
|
Assignee: |
Industrial Technology Research
Institute
Hsinchu
TW
|
Family ID: |
59974241 |
Appl. No.: |
15/659434 |
Filed: |
July 25, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 4/043 20130101;
H01M 10/056 20130101; H01M 4/762 20130101; H01M 4/661 20130101;
H01M 10/054 20130101; H01M 4/808 20130101; Y02E 60/10 20130101;
H01M 4/0423 20130101; Y02E 60/13 20130101; H01M 4/133 20130101;
H01M 2300/0045 20130101; H01M 4/587 20130101; H01M 4/0404 20130101;
H01M 4/1393 20130101 |
International
Class: |
H01M 4/80 20060101
H01M004/80; H01M 10/054 20060101 H01M010/054; H01M 4/587 20060101
H01M004/587; H01M 4/133 20060101 H01M004/133; H01M 4/66 20060101
H01M004/66; H01M 10/056 20060101 H01M010/056 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 3, 2016 |
TW |
105131870 |
Claims
1. An electrode, comprising: a main body, wherein the main body
comprises a cavity, and the main body is made of a conductive
network structure; and an active material disposed in the cavity,
wherein the length of the longest side of the particle of the
active material is greater than the length of the longest side of
the pore of the conductive network structure, such that the active
material is confined in the conductive network structure.
2. The electrode as claimed in claim 1, wherein the conductive
network structure comprises a metal three-dimensional foaming
network structure, or a metal network structure.
3. The electrode as claimed in claim 2, wherein a material of the
metal three-dimensional foaming network structure is foaming
nickel, foaming iron, foaming copper, foaming titanium, foaming
cobalt, or a foaming alloy thereof.
4. The electrode as claimed in claim 2, wherein a material of the
metal network structure is nickel net, iron net, copper net,
titanium net, cobalt net, or an alloy net thereof.
5. The electrode as claimed in claim 1, wherein the active material
comprises a layered active layer or an agglomeration of a layered
active layer.
6. The electrode as claimed in claim 1, wherein the active material
is graphite, carbon nanotube, graphene, or a combination
thereof.
7. The electrode as claimed in claim 1, wherein the conductive
network structure has a porosity from 50% to 98%.
8. The electrode as claimed in claim 1, wherein the length of the
longest side of the pore of the conductive network structure is
from 1 nm to 1 mm.
9. The electrode as claimed in claim 1, wherein the active material
is present at a level that is equal to or greater than 50% of the
cavity by volume.
10. The electrode as claimed in claim 1, further comprising: a
first active layer disposed on an inner surface of the conductive
network structure.
11. The electrode as claimed in claim 10, further comprising: a
second active layer disposed on an outer surface of the conductive
network structure.
12. A device, comprising: a first electrode, wherein the first
electrode is the electrode as claimed in claim 1; a first
separator; and a second electrode, wherein the first separator
disposed between the first electrode and the second electrode.
13. The device as claimed in claim 12, further comprising: a third
metal electrode, wherein the first electrode is disposed between
the second electrode and the third metal electrode; and a second
separator, wherein the second separator is disposed between the
first electrode and the third metal electrode.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The application is based on, and claims priority from,
Taiwan Application Serial Number 105131870, filed on Oct. 3, 2016,
the disclosure of which is hereby incorporated by reference herein
in its entirety.
TECHNICAL FIELD
[0002] The technical field relates to an electrode and a device
employing the same.
BACKGROUND
[0003] Aluminum is the most abundant metal on earth and the third
most abundant element in the earth's crust. An aluminum-based redox
couple, which involves three electron transfers during
electrochemical charge and discharge reactions, provides storage
capacity that is competitive with that of a single-electron
lithium-ion battery. Additionally, because of its lower reactivity
and flammability in comparison with lithium, such an aluminum-ion
battery might offer significant safety improvements.
[0004] Given the foregoing enhanced theoretical capacity of an
aluminum-ion battery, aluminum-ion battery constructions are
desirable in that they may feasibly and reliably provide enhanced
battery performance, such as enhanced capacity and discharge
voltage.
[0005] The capacity of an aluminum-ion battery is proportional to
the amount of graphite in the aluminum-ion battery. The positive
electrode of a conventional aluminum-ion battery includes a
current-collecting substrate and a graphite material bonded on the
current-collecting substrate via an adhesive agent. The adhesive
agent, however, not only reduces the electrical conductivity
between the current-collecting substrate and the active material
but also lengthens the processing time of the positive electrode.
Furthermore, due to the adhesive agent, the graphite material
located in the deeper position near the current-collecting
substrate will not be infiltrated by the electrolyte.
[0006] Hence, it is against this background that a need arose to
develop embodiments of this disclosure.
SUMMARY
[0007] According to embodiments of the disclosure, the disclosure
provides an electrode. The electrode can include a main body and an
active material. The main body comprises a cavity, and the main
body is made of a conductive network structure. The active material
is disposed in the cavity, wherein the length of the longest side
of the particle of the active material is greater than the length
of the longest side of the pore of the conductive network
structure.
[0008] According to other embodiments of the disclosure, the
disclosure provides a device. The device includes a first
electrode, a first separator, and a second electrode, wherein the
first electrode is the aforementioned electrode, and wherein the
first separator is disposed between the first electrode and the
second electrode.
[0009] A detailed description is given in the following embodiments
with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a perspective view of the electrode according to
an embodiment of the disclosure;
[0011] FIG. 2 is a cross-sectional view along line 2-2' of the
electrode shown in FIG. 1;
[0012] FIG. 3 is an enlarged view of the region 3 of the electrode
shown in FIG. 2;
[0013] FIG. 4 is an enlarged view of the region 3 of the electrode
shown in FIG. 2 according to other embodiments;
[0014] FIG. 5 is a cross-sectional view of the electrode according
to another embodiment;
[0015] FIG. 6 is a cross-sectional view of the electrode according
to other embodiments;
[0016] FIG. 7 is a cross-sectional view of the device according to
some embodiments;
[0017] FIG. 8 is a photograph showing the appearance of the
graphite electrode of Example 1;
[0018] FIGS. 9-12 are graphs showing the results of cycling
stability tests of the aluminum-ion batteries according to Examples
1 and 2, and Comparative Example 2.
[0019] FIG. 13 is a photograph showing the appearance of the
graphite electrode of Example 3; and
[0020] FIGS. 14-15 are graphs showing the results of cycling
stability tests of the aluminum-ion batteries according to Examples
3 and 4.
DETAILED DESCRIPTION
[0021] In the following detailed description, for the purposes of
explanation, numerous specific details are set forth in order to
provide a thorough understanding of the disclosed embodiments. It
will be apparent, however, that one or more embodiments may be
practiced without these specific details. In other instances,
well-known structures and devices are shown schematically in order
to simplify the drawing.
[0022] The disclosure provides an electrode (such as a positive
electrode of the metal-ion battery) and a device (such as a
metal-ion battery) employing the same. The electrode includes a
main body and an active material. The main body, having a cavity,
is made of a conductive network structure, and the active material
is disposed in the cavity. Since the length of the longest side of
the particle of the active material is greater than the length of
the longest side of the pore of the conductive network structure
and the Van der Waals force exists between the active materials,
the active material may be confined in the cavity surrounded by the
conductive material having a network structure, thereby forming an
electrode having a tea bag-like sealed structure. As a result, the
active material of the disclosure can be bonded in the conductive
network structure in the absence of an adhesive agent. Therefore,
the performance of the battery of the disclosure would not be
deteriorated by an adhesive agent, and the complexity of the
process for fabricating the electrode can be reduced. Since the
active material of the electrode is encapsulated by the conductive
network structure, the active material disposed in the cavity is
apt to be infiltrated by the electrolyte, thereby increasing the
utilization rate of the active material and increasing the storage
capacity and the total capacity generation of the device employing
the electrode. On the other hand, an active layer can be further
disposed on the surface of the conductive network structure to
cover the surface of the conductive network structure. As a result,
the loading amount of the active material of the electrode can be
increased. Furthermore, due to the Van der Waals force between the
active layer disposed on the sidewall of the cavity and the active
material disposed in the cavity, the conductive material has a
network structure that can combine closely with the active
material, thereby enhancing current conduction of the electrode and
increasing the specific capacity of the device employing the
electrode during charging and discharging at high current
density.
[0023] FIG. 1 is a perspective view of the electrode 100 according
to an embodiment of the disclosure. As shown in FIG. 1, the
electrode 100 includes a main body 10 (such as a plate-shaped main
body or a sheet-shaped main body) and an active material 12. FIG. 2
is a cross-sectional view along line 2-2' of the electrode 100
shown in FIG. 1. As shown in FIG. 2, the main body 10 includes a
cavity 11, and the active material 12 is disposed in the cavity 11.
Namely, the active material 12 is encapsulated in the main body 10.
According to embodiments of the disclosure, the active material 112
can be present at a level that is equal to or greater than 50% of
the cavity by volume, such as between 50% and 98% of the cavity by
volume. The main body 10 can be a conductive network structure.
Therefore, the active material is encapsulated by the conductive
network structure (such as a conductive material having a network
structure). As a result, the electrolyte can freely pass through
the conductive network structure, and thus the active material in
the cavity can be infiltrated more conveniently. As shown in FIG.
2, the main body 10 can have a thickness T1 from about 50 nm to 10
mm, such as from about 100 nm to 5 mm, from about 200 nm to 4 mm,
or from about 500 nm to 1 mm. The cavity can have a thickness T2
from about 10 nm to 8 mm, such as from about 20 nm to 5 mm.
Furthermore, the thickness T2 of the cavity can be adjusted to meet
practical requirements.
[0024] According to embodiments of the disclosure, suitable
materials for the conductive network structure can be a foaming
metal material 14. FIG. 3 is an enlarged view of the region 3 of
the electrode shown in FIG. 2. As shown in FIG. 3, the main body 10
can be made of a foaming metal material 14 (such as foaming nickel,
foaming iron, foaming copper, foaming cobalt, foaming titanium, or
a foaming alloy thereof (such as a foaming alloy including nickel,
iron, copper, cobalt, and/or titanium). The foaming metal material
14 can include a plurality of pores 13, and the pores 13 are
distributed three-dimensionally within the metal foaming material
14. Therefore, the pores 13 may be interconnected with each other
to form an irregular-geometric-shaped and slender pore, and the
metal foaming material 14 can have a sponge-like configuration. In
order to encapsulate the active material 12 with a metal foaming
material 14, the length of the longest side of the particle of the
active material is greater than the length of the longest side of
the pore of the conductive network structure. For example, the
length of the longest side of the pore of the conductive network
structure can be from about 1 nm to 1 mm. Therefore, the active
material 12 cannot be detached from the cavity 11 via the pore 13
of the metal foaming material 14. Namely, the particle of the
active material 12 cannot pass through the metal foaming material
14 via the pore 13, and the active material 12 is completely
confined in the cavity 11 of the main body 10. A porosity of the
foaming metal material can be greater than about 50%, such as from
about 50% to 98%. The porosity may be the quotient of the volume of
the pores over the total volume of the pores and the metal foaming
material.
[0025] According to embodiments of the disclosure, the conductive
network structure can be metal net 16. FIG. 4 is an enlarged view
of the region 3 of the electrode 100 shown in FIG. 2 according to
other embodiments. As shown in FIG. 4, the main body 10 can be made
of a metal net 16, such as a nickel net, iron net, copper net,
titanium net, cobalt net, or an alloy net thereof. The metal net 16
has a plurality of pores 15, and each pore 15 can be polygonal,
circular, elliptic, irregular geometric, or a combination
thereof.
[0026] The plurality of pores 15 can be separate from each other.
The active material 12 does not pass through the metal net via the
pores 15 of the metal net 16. Namely, the length of the longest
side of the particle of the active material is greater than the
length of the longest side of the pore 15 of the metal net 16. For
example, the length of the longest side of the pore of the metal
net 16 is from about 1 nm to 1 mm. Therefore, the active material
12 cannot be detached from the cavity 11 via the pore 15 of the
metal net 16, and the active material 12 is completely confined in
the cavity 11 of the main body 10. A porosity of the metal net can
be greater than about 50%, such as from about 50% to 98%. The
porosity may be the quotient of the volume of the pores over the
total volume of the pores and the metal net.
[0027] According to embodiments of the disclosure, the active
material includes a layered active layer or an agglomeration of a
layered active layer. According to embodiments of the disclosure,
the active material can be an intercalated carbon material, such as
graphite (including natural graphite, artificial graphite,
mesophase carbon microbeads, pyrolytic graphite, foaming graphite,
flake graphite, or expanded graphite), multilayer graphene,
graphene, carbon nanotube or a combination thereof. According to
embodiments of the disclosure, the active material can be layered
double hydroxide), layered oxide, layered chalcogenide or a
combination thereof. The active material (such as powder, sheet, or
strip), which does not pass through the pore of the conductive
network structure, is selected, in order to ensure that the active
material is confined in the cavity of the main body. In the
selection of the active material, the active material can be
disposed in a bowl-shaped carrier made of the conductive network
structure in advance, and then the active material disposed in the
bowl-shaped carrier is subjected to a vibration for a period of
time (such as 1-100 hr) to observe whether the active material
passes through the pore of the conductive network structure. If
there is no active material which is detached from the bowl-shaped
carrier, it means that the active material cannot pass through the
pore of a main body made of the conductive network structure.
[0028] FIG. 5 is a cross-sectional view of the electrode according
to another embodiment. As shown in FIG. 5, a first active layer 18
can be further disposed on an inner surface of the cavity 11. Thus,
a Van der Waals force between the first active layer 18 and the
active material 12 disposed in the cavity 11 is generated, thereby
facilitating the main body 10 (i.e. the conductive material having
a network structure) to combine closely with the active material
12. The first active layer 18 can be a graphite. The first active
layer 18 can be formed on the conductive material having a network
structure by chemical vapor deposition, and then the active
material 12 is encapsulated in the conductive material. In
addition, FIG. 6 is a cross-sectional view of the electrode
according to other embodiments. As shown in FIG. 6, a second active
layer 20 can be further disposed on an outer surface of the main
body 10 (i.e. the conductive material having a network structure).
The second active layer 20 can also be a graphite. The second
active layer 20 can be formed on the main body 10 during the
formation of the first active layer 18. Namely, the first active
layer 18 and the second active layer 20 can be made of the same
material and formed in the same process. In addition, the diameter
of the pore of the conductive material having a network structure
can be shrunk after the deposition of the first active layer and
the second active layer.
[0029] The electrode of the disclosure can be formed in the
following steps. First, a sheet made of the conductive network
structure is provided. Next, the sheet is folded, and the active
material is disposed in the spatial area of the folding sheet.
According to embodiments of the disclosure, before folding the
sheet, the sheet can be subjected to a deposition to form an active
layer on the surface of the sheet. Next, the folding sheet having
the active material is subjected to a lamination or a spot welding
process to form a main body having a cavity, in order to
encapsulate the active material in the cavity. After the lamination
or a spot welding process, the folding sheet having the active
material can be subjected to a rolling compaction, in order to
force the active material to be distributed among the spatial area
of the folding sheet and closely combine the active material with
the conductive material (i.e. the conductive network structure). In
addition, according to other embodiments of the disclosure, the
electrode of the disclosure can be formed in the following steps.
First, a first sheet and a second sheet made of the conductive
network structure are provided, wherein the first sheet and the
second sheet are the same size. The active material is disposed on
the first sheet, and then the second sheet is covered on the first
sheet, obtaining a stack of sheets. Next, the stack of sheets is
subjected to a lamination or a spot welding process to form a main
body having a cavity. Thus, the active material is encapsulated in
the cavity.
[0030] According to embodiments of the disclosure, the disclosure
also provides a device, such as a metal-ion battery, or a
capacitor. FIG. 7 is a cross-sectional view of the device 200
according to some embodiments. As shown in FIG. 7, the device 200
includes a first electrode 101, a first separator 102, and a second
electrode 103, wherein the first electrode 101 is the
aforementioned electrode of the disclosure, and the first separator
102 is disposed between the first electrode 101 and the second
electrode 103. The device 200 can include an electrolyte 105,
wherein the electrolyte 105 is disposed between the first electrode
101 and the second electrode 103. The device 200 can be a
rechargeable secondary battery, although primary batteries also are
encompassed by the disclosure.
[0031] According to embodiments of the disclosure, the device of
the disclosure can further include a third electrode and a second
separator, wherein the first electrode is disposed between the
second electrode and the third metal electrode, and the second
separator is disposed between the first electrode and the third
electrode.
[0032] According to embodiments of the disclosure, the device 200
can be an aluminum-ion battery. In an embodiment of the disclosure,
the battery 100 is an aluminum-ion battery, although other types of
metal-ion batteries are encompassed by the disclosure. The second
electrode 103 includes aluminum, such as a non-alloyed form of
aluminum or an aluminum alloy. More generally, a suitable material
of the second electrode 103 can include one or more of an alkali
metal (e.g., lithium, potassium, sodium, and so forth), an alkaline
earth metal (e.g., magnesium, calcium, and so forth), a transition
metal (e.g., zinc, iron, nickel, cobalt, and so forth), a main
group metal or metalloid (e.g., aluminum, silicon, tin, and so
forth), or a metal alloy of two or more of the foregoing elements
(e.g., an aluminum alloy).
[0033] The first separator 102 can mitigate against electrical
shorting of the first electrode 101 and the second electrode 103,
and the electrolyte 105 can support reversible deposition and
dissolution (or stripping) of the first electrode 101, and
reversible intercalation and de-intercalation of anions at the
first electrode 101. The electrolyte 105 can include an ionic
liquid, which can support reversible redox reaction of a metal or a
metal alloy included in the second electrode 103.
[0034] Examples of ionic liquids can be urea, N-methylurea, choline
chloride, ethylchlorine chloride, alkali halide, dimethyl sulfone,
methylsulfonylmethane, alkylimidazolium salt, alkylpyridinium salt,
alkylfluoropyrazolium salt, alkyltriazolium salt, aralkylammonium
salt, alkylalkoxyammonium salt, aralkylphosphonium salt,
aralkylsulfonium salt, alkylguanidinium salt or mixtures thereof.
For example, the electrolyte 105 can correspond to, or can include,
a mixture of an aluminum halide and an ionic liquid, and a molar
ratio of the aluminum halide and the ionic liquid is at least about
1.1 or 1.2, up to about 1.5, 1.8, or more, such as where the
aluminum halide is AlCl.sub.3, the ionic liquid is
1-ethyl-3-methylimidazolium chloride, and the molar ratio of the
aluminum chloride to 1-ethyl-3-methylimidazolium chloride is
greater than about 1.2. An ionic liquid electrolyte can be doped
(or have additives added) to increase electrical conductivity and
lower viscosity, or can be otherwise altered to yield compositions
that favor the reversible electrodeposition of metals.
[0035] Below, exemplary embodiments will be described in detail
with reference to the accompanying drawings so as to be easily
realized by a person having ordinary knowledge in the art. The
inventive concept may be embodied in various forms without being
limited to the exemplary embodiments set forth herein. Descriptions
of well-known parts are omitted for clarity, and like reference
numerals refer to like elements throughout.
EXAMPLES
Example 1
[0036] First, a foaming nickel sheet (having a size of 70
mm.times.70 mm, a thickness of 0.2 mm, a porosity of 90%, and a
pore diameter of about 200 .mu.m) was provided. Next, the foaming
nickel sheet was folded, and 125 mg of expanded graphite (the
length of the longest side of the expanded graphite was 400-500
.mu.m) was uniformly distributed on the spatial area of the folding
sheet. Next, the folding sheet was subjected to a welding process
to close the opening along the edge of the folding sheet in order
to encapsulate the active material in the cavity of the foaming
nickel sheet. Next, the folding nickel sheet was subjected to
lamination by a calender mill, thereby closely combining the
foaming nickel with the expanded graphite. Herein, the expanded
graphite was agglomerated into an agglomeration due to the Van der
Waals force. Therefore, a graphite electrode (having a size of 35
mm.times.70 mm) was formed, as shown in FIG. 8.
[0037] Next, an aluminum foil (with a thickness of 0.03 mm,
manufactured by Alfa Aesar) was cut to obtain aluminum electrodes
(having a size of 35 mm.times.70 mm). Next, separators (two layers
of 8.times.9 cm.sup.2 with trade No. Whatman) were provided. Next,
the aluminum electrode, the separator, the graphite electrode, the
separator, and the aluminum electrode were placed in sequence and
sealed within an aluminum plastic pouch. Next, an electrolyte
(including aluminum chloride (AlCl.sub.3) and
1-ethyl-3-methylimidazolium chloride ([EMIm]Cl), wherein the molar
ratio between AlCl.sub.3 and [EMIm]Cl was about 1.4) was injected
into the aluminum plastic pouch, obtaining the aluminum-ion battery
(1).
[0038] Next, the aluminum-ion battery (1) of Example 1 was charged
(to about 2.45V) and discharged (to about 1V) at a current density
of about 1000 mA/g by a NEWARE battery analyzer to analyze the
performance thereof, and the results are shown in FIG. 9 and Table
1.
Example 2
[0039] Example 2 was performed in the same manner as Example 1
except that the amount of the expanded graphite was increased from
125 mg to 140 mg. Thus, an aluminum-ion battery (2) was
obtained.
[0040] Next, the aluminum-ion battery (2) of Example 1 was charged
(to about 2.45V) and discharged (to about 1V) at a current density
of about 1000 mA/g by a NEWARE battery analyzer to analyze the
performance thereof, and the results are shown in FIG. 10 and Table
1.
Comparative Example 1
[0041] First, a foaming nickel sheet (having a size of 35
mm.times.70 mm, a thickness of 0.2 mm, a porosity of 90%, and a
pore diameter of about 200 .mu.m) was provided. Next, a coating of
a composition was formed on the surface of the foaming nickel sheet
by coating. The composition included 200 mg of expanded graphite
powder, 22 mg of adhesive (polyacrylic acid), and a solvent
(N-methyl-2-pyrrolidone). Next, the foaming nickel sheet was baked
in a vacuum furnace at 100.degree. C. After baking for 2 days, a
graphite electrode was obtained.
[0042] Next, an aluminum foil (with a thickness of 0.03 mm,
manufactured by Alfa Aesar) was cut to obtain aluminum electrodes
(having a size of 35 mm.times.70 mm). Next, separators (two layers
of 8.times.9 cm.sup.2 with trade No. Whatman) were provided. Next,
the aluminum electrode, the separator, the graphite electrode, the
separator, and the aluminum electrode were placed in sequence and
sealed within an aluminum plastic pouch. Next, an electrolyte
(including aluminum chloride (AlCl.sub.3) and
1-ethyl-3-methylimidazolium chloride ([EMIm]Cl), wherein the molar
ratio between AlCl.sub.3 and [EMIm]Cl was about 1.4) was injected
into the aluminum plastic pouch, obtaining the aluminum-ion battery
(3).
[0043] Next, the aluminum-ion battery (3) of Example 1 was charged
(to about 2.45V) and discharged (to about 1V) at a current density
of about 1000 mA/g by a NEWARE battery analyzer to analyze the
performance thereof, and the results are shown in FIG. 11 and Table
1.
Comparative Example 2
[0044] First, a carbon paper (having a size of 35 mm.times.70 mm)
was provided. Next, a composition including 121 mg, of expanded
graphite powder, 13.4 mg of adhesive (polyacrylic acid), and a
solvent (N-methyl-2-pyrrolidone) was provided. Next, a coating of
the composition was formed on the surface of the carbon paper by
blade coating. Next, the carbon paper was baked in a vacuum furnace
at 100.degree. C. After baking for 2 days, a graphite electrode was
obtained.
[0045] Next, an aluminum foil (with a thickness of 0.03 mm,
manufactured by Alfa Aesar) was cut to obtain aluminum electrodes
(having a size of 35 mm.times.70 mm). Next, separators (two layers
of 8.times.9 cm.sup.2 with trade No. Whatman) were provided. Next,
the aluminum electrode, the separator, the graphite electrode, the
separator, and the aluminum electrode were placed in sequence and
sealed within an aluminum plastic pouch. Next, an electrolyte
(including aluminum chloride (AlCl.sub.3) and
1-ethyl-3-methylimidazolium chloride ([EMIm]Cl), wherein the molar
ratio between AlCl.sub.3 and [EMIm]Cl was about 1.4) was injected
into the aluminum plastic pouch, obtaining the aluminum-ion battery
(4).
[0046] Next, the aluminum-ion battery (4) of Example 1 was charged
(to about 2.45V) and discharged (to about 1V) at a current density
of about 1000 mA/g by a NEWARE battery analyzer to analyze the
performance thereof, and the results are shown in FIG. 12 and Table
1.
TABLE-US-00001 TABLE 1 graphite load of the graphite electrode
specific (mg) capacity (mAh/g) Example 1 125 ~62 Example 2 140 ~62
Comparative 200 ~37 Example 1 Comparative 121 ~29.4 Example 2
[0047] As shown in Table 1, the graphite electrodes of Examples 1
and 2 included the expanded graphite powder encapsulated in the
conductive material having a network structure (foaming nickel),
and no adhesive agent exists in the graphite electrodes. Therefore,
the electrolyte of the battery can freely pass through the
conductive network structure, and thus the expanded graphite in the
cavity can be more conveniently infiltrated by the electrolyte. As
a result, the specific capacity of the aluminum-ion battery (2) was
maintained even when the graphite load was increased (from 125 mg
to 140 mg). In addition, the aluminum-ion batteries (3) and (4),
having high graphite load of the graphite electrode, as disclosed
in Comparative Examples 1 and 2, exhibit low specific capacity due
to the use of the adhesive agent. Therefore, compared with
Comparative Examples 1 and 2 employing the adhesive agent, the
complexity of the process for fabricating the electrode disclosed
in Examples 1 and 2 is reduced since the baking process for
removing the solvent of the coating composition has been omitted,
and the performance of the battery disclosed in Examples 1 and 2 is
not deteriorated by the adhesive agent.
Example 3
[0048] First, a foaming nickel sheet (having a size of 70
mm.times.70 mm, a thickness of 0.2 mm, a porosity of 90%, and a
pore diameter of about 200 .mu.m) was provided. Next, the foaming
nickel sheet was disposed in a vacuum furnace, and a vapor
deposition was performed in the presence of methane (as reaction
source gas) and hydrogen and argon (as carrier gas) at
900-1100.degree. C. to form a graphite layer (40 mg) covering on
the surface of the foaming nickel sheet.
[0049] Next, the foaming nickel sheet was folded, and 51 mg of
expanded graphite (the length of the longest side of the expanded
graphite was 400-500 .mu.m) was uniformly distributed on the
spatial area of the folding sheet. Next, the folding sheet was
subjected to a welding process to close the opening along the edge
of the folding sheet in order to encapsulate the active material in
the cavity of the foaming nickel sheet. Next, the folding nickel
sheet was subjected to a lamination by a calender mill, thereby
closely combining the foaming nickel sheet with the expanded
graphite. Herein, the expanded graphite was agglomerated into an
agglomeration due to the Van der Waals force. Therefore, a graphite
electrode (having a size of 35 mm.times.70 mm) was formed, as shown
in FIG. 13.
[0050] Next, an aluminum foil (with a thickness of 0.03 mm,
manufactured by Alfa Aesar) was cut to obtain aluminum electrodes
(having a size of 35 mm.times.70 mm). Next, separators (two layers
of 8.times.9 cm.sup.2 with trade No. Whatman) were provided. Next,
the aluminum electrode, the separator, the graphite electrode, the
separator, and the aluminum electrode were placed in sequence and
sealed within an aluminum plastic pouch. Next, an electrolyte
(including aluminum chloride (AlCl.sub.3) and
1-ethyl-3-methylimidazolium chloride ([EMIm]Cl), wherein the molar
ratio between AlCl.sub.3 and [EMIm]Cl was about 1.4) was injected
into the aluminum plastic pouch, obtaining the aluminum-ion battery
(5).
[0051] Next, the aluminum-ion battery (5) of Example 3 was charged
(to about 2.45V) and discharged (to about 1V) at a current density
of about 1000 mA/g by a NEWARE battery analyzer to analyze the
performance thereof, and the results are shown in FIG. 14 and Table
2.
Example 4
[0052] Example 4 was performed in the same manner as Example 3
except that the amount of the graphite layer was increased from 40
mg to 51 mg, and the amount of the graphite was increased from 51
mg to 96 mg. Thus, an aluminum-ion battery (6) was obtained.
[0053] Next, the aluminum-ion battery (6) of Example 4 was charged
(to about 2.45V) and discharged (to about 1V) at a current density
of about 1000 mA/g by a NEWARE battery analyzer to analyze the
performance thereof, and the results are shown in FIG. 15 and Table
2.
TABLE-US-00002 TABLE 2 graphite load of the graphite electrode
specific capacity (mg) (mAh/g) Example 3 91 ~83 Example 4 147
~83
[0054] The graphite electrodes of the aluminum-ion batteries (5)
and (6) as disclosed in Examples 3 and 4 further include a graphite
layer deposited and covered on the surface of the nickel foaming.
As a result, the active material loading amount of the electrode is
increased, and the foaming nickel sheet is closely combined with
the expanded graphite due to the Van der Waals force between the
graphite layer and the expanded graphite encapsulated in the
foaming nickel. Thus, the current conduction of the electrode is
enhanced, and the specific capacity (83 mAh/g) of the aluminum-ion
batteries (5) and (6) employing the electrode is increased during
charging and discharging at high current density. In addition, the
graphite electrodes of Examples 3 and 4 included the expanded
graphite powder encapsulated in the conductive material having a
network structure (foaming nickel having a graphite layer), and no
adhesive agent exists in the graphite electrodes. Therefore, the
electrolyte of the battery can freely pass through the conductive
network structure, and thus the expanded graphite in the cavity can
be more conveniently infiltrated by the electrolyte. As a result,
the specific capacity of the aluminum-ion battery (6) was
maintained even when the graphite load was increased (from 91 mg to
147 mg), and thus the total capacity of the aluminum-ion battery is
increased. Conversely, the electrolyte would not infiltrate the
active material when the conductive material does not have a
network structure. Therefore, the capacity would not be increased
even though the graphite load increases.
[0055] It will be clear that various modifications and variations
can be made to the disclosed methods and materials. It is intended
that the specification and examples be considered as exemplary
only, with the true scope of the disclosure being indicated by the
following claims and their equivalents.
* * * * *